With the ever-increasing popularity and competitiveness of golf, substantial effort and resources are currently being expended to improve golf clubs so that increasingly more golfers can have more fun and more success at playing golf. Much of this improvement activity has been in the realms of sophisticated materials and club-head engineering. For example, modern “wood-type” golf clubs (notably, “drivers” and “utility clubs”), with their sophisticated shafts and metal club-heads, bear little resemblance to the “wood” drivers, low-loft long-irons, and higher numbered fairway woods used years ago. These modern wood-type clubs are generally called “metal-woods.”
An exemplary metal-wood golf club such as a fairway wood or driver typically includes a shaft having a lower end to which a hollow club-head is attached. The club-head usually is made, at least in part, of a light-weight but strong metal such as titanium alloy. The club-head comprises a body to which a face insert (also called “face plate”) is attached. The body typically includes a hosel that extends generally upward and is connected to the shaft of the club. The body also includes a heel region situated close to the hosel, a toe region situated opposite the heel region, a sole (lower) region, and a crown (upper) region. The body bears most of the impact load imparted to the face insert when the club-head strikes a golf ball. The face insert defines a front ball striking surface or strike face that actually contacts the golf ball during a normal golf stroke.
In contrast to wood-type clubs used years ago, the club-heads of many modern metal-woods are hollow, which has been made possible by the use of light-weight, strong metals and other materials for fabricating the club-head. Use of titanium and other light-weight metal alloys has permitted the walls of the club-head to be made very thin, which has permitted the club-heads to be made substantially larger than their predecessors. These oversized club-heads tend to provide a larger “sweet spot” on the face insert and higher club-head inertia, thereby making the club-heads more “forgiving” than smaller club-heads. This “forgiveness” means that a golfer using the club who strikes the ball off the center, or “sweet spot,” of the face insert will still produce a ball trajectory that is substantially similar to the shot that otherwise would have been made if the golfer struck the ball on the sweet spot. Characteristics, such as size of the sweet spot, are determined by many variables including the shape profile, size, and thickness of the face insert as well as the location of the center of gravity (CG) of the club-head.
There are practical limits to the maximum size of club-heads, based on factors such as the particular material of the club-head, the mass of the club-head, and the strength of the club-head. Since the maximal mass of the club-head is limited under United States Golf Association (USGA) rules, as the club-head size is increased, the walls of the body and face plate generally are made correspondingly thinner.
To achieve high rotational moments of inertia, and thus more resistance to twisting or rotation upon impact with a golf ball, and thus more forgiveness, the mass of the club-head is typically distributed as much as possible around the periphery of the club-head and rearward of the face plate. As a result, the club-head's center of gravity generally is located rearwardly from the face plate at a prescribed location, which also helps the club to produce a desired launch angle upon impact with a golf ball.
Another factor in club-head design is the face insert or face plate. Impact of the face plate with the golf ball causes deflection of the face plate. This deflection and the subsequent recoil are measured as the club-head's coefficient of restitution (COR). A thinner face plate generally deflects more at impact than a thicker face plate of the same material. Thus, a club-head having a thin face plate can impart more energy and thus a higher initial velocity (rebound velocity) to a struck golf ball than a club with a thicker, more rigid face plate. This rebound phenomenon is called the “trampoline effect” and is an important determinant of the flight distance of the struck ball. Since face-plate deflection is usually greater in the sweet spot of the face plate, a ball struck by the sweet spot generally will have a higher rebound velocity than a ball struck off-center. Face plates of various thickness configurations have been proposed to adjust the characteristics of the face plate. For example, face plates can have a thicker center portion or a thin central portion surrounded by a thicker ring portion. Because of the importance of the trampoline effect, the COR of clubs is limited under USGA rules.
Wood-type drivers often are provided with score line grooves extending into the striking surface of the golf club head. Grooves on a wood-type driver club have little impact on the flight of the golf ball, except under wet conditions. However, they are often used by a golfer to line up a golf shot prior to swinging the club. To make these score line grooves more visible, paint has been used to partially fill the grooves, making them more visible. The paint is protected somewhat from being worn off by being recessed into the grooves from the outermost ball striking surface. Nevertheless, there is some risk of the paint being worn off.
In addition, some golf clubs have been provided with face inserts comprising a composite material impregnated with resin. Such materials can be prone to scratching.
Therefore, the need exists for an improved golf club head, a face insert therefor, and a method of manufacturing thereof.